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  • 11
    Electronic Resource
    Electronic Resource
    Computer simulation of Bragg and diffuse scattering intensities against temperature for a structural phase transition (1987)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 43 (1987), S. 690-694 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Molecular dynamics has been used to estimate the properties of a two-dimensional crystal exhibiting a second-order soft-mode phase transition. Using a vibrational potential for the crystal which is temperature independent, the essential features observed experimentally in the coherent scattering from analogous real systems are reproduced in the computer simulation. The potential consists of an effective one-particle component with multiple minima and a harmonic nearest-neighbour coupling component. It is emphasized that the coupling component is essential to reproduce correctly the qualitative features not only of the diffuse scattering, but also of the mean-square displacements as a function of temperature. The condition for appearance of a cusp at TC in the mean-square displacement versus temperature curve is discussed and the formation of superlattice peaks in the diffuse scattering is demonstrated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767387098726
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    Paper (German National Licenses)
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  • 12
    Electronic Resource
    Electronic Resource
    On the X-ray or neutron diffraction determination of atomic position parameters (1981)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 37 (1981), S. 264-266 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: It is shown that, unless the atomic position parameters in a crystal are completely determined by symmetry, the position parameters corresponding to the minimum of the potential in the thermally strained lattice differ from those corresponding to thermodynamic equilibrium. By appropriate refinement of X-ray or neutron diffraction data, it is possible to obtain both sets of position parameters as well as the linear and higher-order coefficients of one-particle potentials expanded about the equilibrium positions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739481000582
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    Paper (German National Licenses)
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  • 13
    Electronic Resource
    Electronic Resource
    Thermal vibration in CsSCN below the structural phase transition at 470 K (1987)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 43 (1987), S. 16-23 
    Details
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108768187098367
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    Paper (German National Licenses)
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  • 14
    Electronic Resource
    Electronic Resource
    The electron distribution of the hydroxide ion in lithium hydroxide (1978)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 34 (1978), S. 542-547 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Analysis of recently published X-ray and neutron diffraction data for LiOH reveals that there are pronounced non-spherical deformations of the electrondensity about the oxygen pseudo-atom. Comparison with a theoretical calculation of the electron density for the isolated hydroxide ion shows that these deformations are due to π-like bonding of the oxygen to the neighbouring hydrogen pseudo-atom. The observed features have shapes consistent with the non-spherical electron distribution of an isolated hydroxide ion undergoing rigid-body libration and translation. It is shown that an important effect of the rigid-body libration is a reversal in sign of the effective quadrupole component of the oxygen pseudo-atom electron density.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739478001151
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    Paper (German National Licenses)
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